Date of Graduation

2004

Document Type

Thesis

Degree Type

MS

Committee Chair

J. Todd Petty

Abstract

I examined relationships between landscape physiographic factors and summer stream temperatures in the Cheat River watershed, WV and developed statistical models to characterize thermal patterns at the stream segment and watershed scales. I also examined the influence of modeled thermal regimes on the distribution of smallmouth bass (Micropterus dolomieui) and brook trout (Salvelinus fontinalis) in this system. The objectives of this study were to (1) develop and verify an empirical model to predict stream temperature at the stream segment scale in the Cheat River basin, (2) quantify the geography of thermal regimes within the basin at the segment and watershed scales, and (3) examine how stream temperature and the geography of drainage networks interact to influence brook trout and smallmouth bass distributions in this system. To address these objectives, I obtained continuous summertime measures of water temperature at 52 sites distributed throughout the Cheat River watershed to calculate two important summer thermal statistics: weekly mean July temperature (WMJT, Wehrly et al. 2003) and maximum weekly average temperature (MWAT, Eaton et al. 1995). By combining landscape variables derived from spatial datasets using Geographic Information Systems (GIS) software with the thermal metrics calculated for each site, I developed multiple-regression models relating summertime thermal regimes to landscape features. These statistical models were used to create a spatial model of WMJT throughout the watershed at the stream segment scale using GIS software. Additionally, a coldwater tributary density spatial layer was created using a GIS software density function in order to characterize the regional thermal regime of each segment based on the number of coldwater tributaries within a 5 km radius of a segment. These base spatial layers were used to quantify and characterize the spatial arrangement of thermal regimes throughout the basin at multiple scales. Similarly, these models were used to characterize and analyze the distribution of brook trout and smallmouth bass in the basin as related to the geography of thermal regimes. This study produced the following results. First, basin area, elevation and gradient accounted for a large degree (R2 = .74) of the variation in summer thermal patterns among stream segments in the Cheat River watershed. Second, the composition and spatial arrangement of coldwater, coolwater, and warmwater segments among watersheds was highly variable in the basin, even among watersheds of similar area. Third, both brook trout and smallmouth bass distributions in the Cheat River watershed were significantly related to modeled summer water temperature, however, there was an unusually high degree of sympatry between these two species in the watershed (11% of all presences for both species), which may be related to the thermal geography of the basin. Finally, brook trout distribution in the Cheat watershed may be related to both local and regional thermal conditions, because the presence of brook trout in warmwater streams was significantly related to the regional density of coldwater tributaries. In conclusion, these results provide further evidence that stream fish communities are influenced simultaneously by local conditions and regional processes.

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